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Download Unit 1: Nutrients & Digestion
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Unit 1: Nutrients & Digestion Chapter 1 Unit 1: Nutrients & Digestion Unit 1 Objectives: Review the 6 basic nutrients and investigate their function Revisit the various digestive systems Comprehend the functions of the digestive anatomy of monogastrics and ruminants Unit 1: Nutrients & Digestion Water Cheapest, most abundant, most important nutrient Constitutes 45-85% of animal body weight decreases with age 90-95% of blood tissue is 70-90% water Unit 1: Nutrients & Digestion Three forms in the body Intracellular • muscle and skin Extracellular • interstitial fluids, lymph, cerebrospinal fluid, blood plasma Urinary and GI water Unit 1: Nutrients & Digestion Functions of Water transportation of nutrients and excrement chemical reactions temperature regulation shape lubrication Water Deficiencies reduced feed intake weight loss/dehydration increased excretion of N and electrolytes Unit 1: Nutrients & Digestion Water sources Drinking water • • • • • temp/humidity affect consumption dietary water affects consumption productivity of the animal affects consumption Water quality is crucial Consumption rates – Swine-2.5-5g/d – Sheep-1-4g/d – Cattle-8-16g/d (may be significantly more in lactation) – Horses-10-14g/d Unit 1: Nutrients & Digestion Water loss urination fecal vaporization from lungs or through skin sweat Water absorption Readily absorbed from virtually all sections of the GI tract • rumen, omasum, ileum, jejunum, cecum, LI Unit 1: Nutrients & Digestion Amount absorbed • varies w/ species and diet • indigestible dietary fiber can reduce absorption • can be reduced by the amount of dietary pectins, toxins, and stressors Carbohydrates (CHO) Consist of Carbon, Hydrogen, Oxygen Unit 1: Nutrients & Digestion Includes: sugars starches cellulose gums CHO makes up 3/4 of plant dry wt. Unit 1: Nutrients & Digestion Classified by the number of sugar molecules Monosaccharides • glucose – most important sugar in nutrition – primary form used for energy • fructose Disaccharides • sucrose • maltose • lactose – milk sugar Unit 1: Nutrients & Digestion Polysaccharides • starch – principle sugar form in cereal grains • cellulose – 25-30% of fibrous plants – most abundant CHO in nature • hemicellulose – main component of plant cell walls – can only be degraded by microbial enzymes – complex mixture of sugars Unit 1: Nutrients & Digestion Non-carbohydrate • Lignin – covers cellulose and hemicellulose to increase rigidity of plant cell walls – as level increases, digestibility decreases – cannot be broken down by any animal or bacterial enzyme Functions source of energy and heat building blocks for other nutrients stored by converting to fat Unit 1: Nutrients & Digestion Deficiencies Ketosis • • • • • • • common in animals requiring high amounts of energy can have a “snowball” effect increases breakdown of protein for energy loss of BW decreases milk production can cause abortion distinct smell of acetone Unit 1: Nutrients & Digestion Diabetes • more common in humans • insufficient insulin production by the pancreas • can be genetically related Digestion & Metabolism Crude Fiber • cellulose, hemicellulose, lignin • Poorly digested Nitrogen-Free Extract • soluble sugars, starches • readily digested Unit 1: Nutrients & Digestion Converted to Adenosine Triphosphate (ATP) • the energy currency of the body • drives all physiological processes that require energy • 1 molecule of glucose will yield 38 ATP’s through various oxidative pathways Lipids Can be soluble or insoluble depending on what they’re mixed with Unit 1: Nutrients & Digestion Classification Simple Lipids • true fats • waxes Compound Lipids • Lipoproteins • Glycolipids • LDL, VLDL, HDL Derived Lipids • Sterols – Cholesterol Unit 1: Nutrients & Digestion • Fatty Acids Essential Fatty Acids • linoleic, linolenic acids Protein Main component of organs and soft structures in the animal body Dietary requirement is highest in young animals Proteins are very large molecules Unit 1: Nutrients & Digestion Protein structure made up of very simple units called Amino Acids (AA) arrangement of AA in the chain and the length of the chain determine the composition of the protein 22 AA are commonly found in proteins • linked together by peptide bonds Unit 1: Nutrients & Digestion Levels of Protein structure Primary Structure • individual AA linked by peptide bonds to form a polypeptide chain Secondary Structure • twisted polypeptide chain • H bonds link helical structures together Tertiary Structure • helical structures fold into rigid layers Unit 1: Nutrients & Digestion Quaternary Structure • several tertiary structures linked together • very large proteins Importance of protein structure • biological activity of the protein related to the level of the protein • Denaturation – loss of protein structure – caused by heat – loses biologic activity, but may increase digestibility Unit 1: Nutrients & Digestion • Maillard Reaction – caused by excess heat – excess heat may be caused by improper storage, cooking, drying, etc. – can severely decrease digestibility Protein Terminology True Protein • made up only of AA Nonprotein Nitrogen (NPN) • not true protein compounds, but contain N, and can be converted to protein • ex.? Unit 1: Nutrients & Digestion Crude Protein • total protein from true and NPN sources • CP = %N x 6.25 Digestible Protein • portion of CP that can be digested • difference between fed protein and fecal protein Essential AA • essential to the animal, and must be supplied in the diet b/c the animal cannot synthesize them fast enough to meet the requirement • PVT TIM HALL Unit 1: Nutrients & Digestion – Phenylalanine, Valine, Threonine, Tryptophan, Isolecine, Methionine, Histidine, Arginine, Leucine, Lysine Functions Basic structural units of the body • collagen • keratin • blood proteins Body Metabolism • enzymes, hereditary transmission • hormones, immune antibodies Unit 1: Nutrients & Digestion Deficiencies reduced growth rate, and feed efficiency infertility, fatty liver, lack of hormone/enzyme production deficiencies/imbalances in AA will decrease production Natural Sources most feeds contain protein quantity and quality of protein may be highly variable Unit 1: Nutrients & Digestion Digestion & Metabolism dietary proteins must be broken down to AA form for absorption • except in early postnatal mammals in the stomach, proteins are broken down to: • dipeptides • tripeptides • free AA Unit 1: Nutrients & Digestion Absorption of proteins • Free AA – absorbed by active transport (requires energy) – occurs in the SI • Di- & Tripeptides – absorbed by mucosal cells in the SI in – will still be changed to FAA • Whole Proteins – engulfed by mucosal cells – only happens in newborn mammals (24-48 hrs.), absorb antibodies from colostrum Unit 1: Nutrients & Digestion Minerals total mineral content of plants often referred to as Ash constitutes 3-5% of animal body dry wt. Classification Macrominerals • present/required in greater levels • Ca, P, K, Mg, Cl, S, Na Unit 1: Nutrients & Digestion Microminerals • present/required in small amounts • Co, Cu, I, Fe, Mn, Mo, Se, Zn Functions • • • • • skeletal formation and maintenance active in protein synthesis oxygen transport fluid balance, and pH activates or components of enzyme systems Unit 1: Nutrients & Digestion Natural Sources forage plants are good natural sources may be somewhat variable Digestion & Metabolism absorbed in the SI in ionic form active transport (Ca, P, Na) or diffusion mineral absorption can vary due to: • age of the animal • form of the element, binding/chelation, excesses or interactions of minerals • pH of GI tract Unit 1: Nutrients & Digestion Vitamins present and active in small amounts essential for tissue development and immune function most cannot be synthesized, and must be supplemented in the diet Unit 1: Nutrients & Digestion Classification Fat-soluble • Vitamins A, D, E, K • regulate metabolism of structural units • absorbed in the SI in the presence of fat Water-soluble • Thiamine, Riboflavin, Niacin, Biotin, Choline, Folic Acid, B12, etc. • concerned with the transfer of energy • absorbed with intestinal water Unit 1: Nutrients & Digestion Digestion & Metabolism little is known about vitamin digestion most absorbed in the upper portion of the intestine • B12 is absorbed in the ileum • water-soluble are readily absorbed • fat-soluble vitamin absorption depends on fat absorption (a slow process) Unit 1: Nutrients & Digestion Nutrients in Metabolism Maintenance Heat for temp regulation energy for internal work minimum movement tissue repair greatest requirement for energy Growth protein, energy and other nutrients required for structural growth Unit 1: Nutrients & Digestion Especially critical when another bodily work is ongoing • lactation, work etc. • growth will be sacrificed in the presence of another need Work mostly requires energy and water Reproduction minimal requirements over or under-conditioning can reduce efficiency Unit 1: Nutrients & Digestion Lactation very high nutritional demand best to feed for lactation demand rather than build up bodily stores Fattening high energy to protein ratio required body will meet all other needs first Called Nutrient Partitioning Unit 1: Nutrients & Digestion Requirements can vary state of growth or age size of animal environment heredity disease activity degree of condition ration imbalances species Unit 1: Nutrients & Digestion Digestive Systems terms to know: Prehension-taking in feed/water Mastication-chewing, reducing particle size Deglutition-swallowing Regurgitation-casting up of undigested material Digestion-breakdown of feed to products for absorption • mechanical, chemical, or enzymatic activity Unit 1: Nutrients & Digestion Absorption-transfer of nutrients from GI to blood/lymph Anabolism-growth or building process Catabolism-breakdown of structures Metabolism-combination of anabolism & catabolism processes in order to create energy Excretion-elimination of wastes Unit 1: Nutrients & Digestion Monogastric Digestive System Mouth what is contained, and what is their functions? Saliva • • • • water-moistens food, aids in taste mucin-lubrication for swallowing Bicarbonate salts-buffer to regulate pH enzymes-amylase can begin breakdown of CHO (only in some species) Unit 1: Nutrients & Digestion Esophagus tube for transport from mouth to stomach moved by muscular contractions called Peristalsis Stomach Cardia-sphincter at junction of esophagus and stomach that regulates passage into/out of stomach Esophageal Region-nongladular, surrounds the cardia Unit 1: Nutrients & Digestion Cardiac Gland Region-produces mucus that protects stomach lining Fundic Gland Region-produces gastric secretions needed to stimulate digestion • hydrochloric acid, and enzymes Pyloric Gland Region-mucus and proteolytic enzymes Pylorus-sphincter controlling passage of digesta to intestine Unit 1: Nutrients & Digestion Functions • feed storage • physical breakdown of material by muscular movement • secretion and regulation of “gastric juices” – acid – pepsinogen – mucus – rennin material leaving stomach now called chyme Unit 1: Nutrients & Digestion Small Intestine Duodenum • receives secretions from pancreas, liver, • active site of digestion Jejunum • active in nutrient absorption Ileum • also active in nutrient absorption walls lined with villi and microville that increase surface area for absorption Unit 1: Nutrients & Digestion Bile • • • • synthesized by the liver, stored in the gall bladder emulsifies fats for absorption activates pancreatic enzymes much is recycled Pancreatic Juice • buffers • digestive enzymes Unit 1: Nutrients & Digestion Large Intestine Cecum • size, and function can vary Colon • largest part Rectum • final section Function • water resorption • can be storage of undigested nutrients Unit 1: Nutrients & Digestion • Can be site of bacterial fermentation • limited site of nutrient absorption Horse Saliva no enzymes scratching from forages stimulates secretions produce ~10g/d Esophagus 50-60” long one-way peristaltic movements Unit 1: Nutrients & Digestion Stomach relatively small stomach, meals must be small little muscular movement Small Intestine no gall bladder to store bile for secretion to SI Large Intestine 60% of GI Unit 1: Nutrients & Digestion Cecum & Large Colon • active bacterial population • breakdown of cellulose and other CHO’s to Volatile Fatty Acids (VFA) acetate, propionate, butyrate for use as energy • synthesize protein and water-soluble vits. Small Colon • primary site of water resorption Unit 1: Nutrients & Digestion Ruminant GI Mouth no upper incisors, upper and lower molars lateral chewing for shredding of forages Saliva • relatively continuous production, more when ruminating or eating • cattle >12 g/d, sheep >2g/d • no enzymes, but sources of N(urea), P, Na • highly buffered Unit 1: Nutrients & Digestion Stomach Reticulum (honeycomb) • esophageal opening of common to both reticulum and rumen • mucus lined walls, no enzyme secretions • moved feed to rumen, omasum • catches any foreign matter • moves feed up esophagus during regurgitation Unit 1: Nutrients & Digestion Rumen • very large, muscular compartment • contains papillae (shag carpet) to increase surface area • functions – storage – soaking – physical breakdown & mixing • very effective fermentation chamber – warm, moist, anaerobic, ideal pH – 25-50b bacteria/mL of rumen fluid Unit 1: Nutrients & Digestion – Production of water-soluble vits. – Production of AA’s & proteins – rumen bacteria also serve as a valuable source of dietary protein & AA’s – rumen bacteria also can digest cellulose & CHO’s to produce VFA’s for use as energy • fully functional by 6-9 wks. of age Omasum • spherical and very muscular • works to reduce particle size of feed before it enters the rest of the GI Unit 1: Nutrients & Digestion Abomasum • first glandular portion of the ruminant GI • very similar to the stomach of the nonruminant Small and Large Intestine very similar to the nonruminant Specialties of the Ruminant GI Esophageal Groove • can direct ingesta directly to the Omasum • doesn’t appear to be functional in the adult Unit 1: Nutrients & Digestion Rumination • allows animal to ingest a lot of feed, then chew at a later time • process: – regurgitation – remastication – resalivation – reswallowing • stimulated by: – particle size – reverse-peristaltic contraction of the rumen/reticulum Unit 1: Nutrients & Digestion • Cud is mostly forage • cattle should ruminate ~8hrs./d Eructation • bacterial fermentation produces large amounts of gas • rumen contractions force gas forward and down to the esophagus • bloat occurs when the gas cannot escape Nutrient Digestion converting feed products into forms that can be absorbed from the GI Unit 1: Nutrients & Digestion Five major areas where digestive enzymes are secreted into the GI Mouth (Saliva) Stomach (Gastric) Pancreas (Duodenum & upper SI) Liver Intestine Unit 1: Nutrients & Digestion Nutrient Absorption Summary nutrient absorption moves digestion products from GI to the blood or lymph system occurs by osmosis through semipermeable membranes Diffusion • molecules move from regions of high concentration to low Active Transport movement of molecules from one region to another w/ the expenditure of energy Unit 1: Nutrients & Digestion Occurs in the SI & LI primarily much VFA absorption in the rumen greatly aided by GI villi Absorption in the Duodenum & Jejunum CHO FAA, di & tripeptides fatty acids minerals vitamins Unit 1: Nutrients & Digestion
